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Etiology and management of stem rot diseases of Stevia
A. KOEHLER (1), H. D. Shew (1). (1) North Carolina State University, Raleigh, NC, U.S.A.

Stevia (<i>Stevia rebaundia</i>) is an herbaceous perennial that is an emerging crop in the US. Stevia is typically grown for 3-5 years and is harvested twice per growing season.  Stevia leaves contain multiple glycosides that are extracted for use as a nonnutritive sweetener which was approved as a food additive by the USDA in 2008. Stevia plantings in North Carolina began in 2011 and are expanding rapidly in the state. Wilting and death of plants in first and second year commercial plantings were observed in NC in 2012 and 2013. <i>Sclerotium rolfsii</i> and <i>Sclerotinia sclerotiorum</i> were observed on diseased plants and Koch’s postulates were performed to verify these organisms as pathogens of Stevia. The biology of these pathogens on Stevia is not yet clearly understood. Initial work is underway to screen Stevia germplasm for resistance to these two stem rot pathogens as well as other potential pathogens that are endemic in Stevia production areas. The goal of this work is to better understand when and where infection is occurring and if any of the genotypes currently available have usable levels of partial resistance. There are currently no products labeled for use on Stevia, which is a limiting factor to the commercial production of Stevia. Fungicide and biocontrol field trials will be conducted to determine optimal application rates and timing.  

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